1. Field of the Invention
The present invention relates to image communication apparatuses and image communication methods. More specifically, the present invention relates to an image communication apparatus such as a facsimile apparatus that allows reception of color information and to an image communication method therefor.
2. Description of the Related Art
When color information is transmitted by a conventional facsimile apparatus, full-color information to be transmitted is JPEG (Joint Photographic Experts Group)-encoded as defined in ITU-T Recommendation T.82 and in Lab color space defined in ITU-T Recommendation T.42.
Recently, use of digital still cameras has become common, so that a demand exists for transmission of color images captured by digital still cameras.
Images captured by digital still cameras have different numbers of pixels in a main scanning direction depending on capture modes and camera types.
In conventional communications via facsimiles, the amount of information in the main scanning direction is determined by a sheet size and a resolution. For example, if the sheet size is A4 and the resolution is 200 dpi, the amount of information in the main scanning direction is determined as 1,728 bits. Thus, transmission of an image having an amount of information other than 1,728 bits is not allowed, requiring processing such as adding white information bits to original information.
Furthermore, according to the conventional art, when color information of a non-regular size is transmitted, the maximum amount of information in the main scanning direction is not defined.
Furthermore, although Lab color space has been used for transmission of color facsimile information, for example, color information captured by a digital still camera is in sYCC color space. Also, color information displayed on a personal computer is in sYCC color space.
Thus, when information captured by a digital camera or information displayed on a personal computer is transmitted via facsimile, information in sYCC color space must first be converted into information in RGB color space and then into information in Lab color space before transmission. The conversion operation is very complex, and causes degradation in the quality of the image information.